There is now a published paper on cats and the rotating snake illusion available at http://www.scirp.org/journal/PaperInformation.aspx?PaperID=48304#.U9togoaltok . The snake illusion is made by Professor Akiyoshi Kitaoka. See his homepage for more nice illusions: http://www.ritsumei.ac.jp/~akitaoka/index-e.html .